U.S. patent number 7,553,905 [Application Number 11/262,639] was granted by the patent office on 2009-06-30 for anti-reflective coatings.
This patent grant is currently assigned to AZ Electronic Materials USA Corp.. Invention is credited to David J. Abdallah, Mark O. Neisser, Jian Yin.
United States Patent |
7,553,905 |
Abdallah , et al. |
June 30, 2009 |
Anti-reflective coatings
Abstract
Novel self-crosslinking polymers are provided and which are
useful in antireflective coatings to reduce outgassing.
Inventors: |
Abdallah; David J.
(Bernardsville, NJ), Yin; Jian (Bridgewater, NJ),
Neisser; Mark O. (Whitehouse Station, NJ) |
Assignee: |
AZ Electronic Materials USA
Corp. (Somerville, NJ)
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Family
ID: |
37886249 |
Appl.
No.: |
11/262,639 |
Filed: |
October 31, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070099108 A1 |
May 3, 2007 |
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Current U.S.
Class: |
525/154; 438/952;
430/271.1 |
Current CPC
Class: |
C08F
220/1807 (20200201); C09D 133/06 (20130101); G03F
7/091 (20130101); C08F 8/30 (20130101); C08F
8/30 (20130101); C08F 212/08 (20130101); C09D
133/06 (20130101); C08L 2666/04 (20130101); C08F
8/30 (20130101); C08F 220/1807 (20200201); Y10S
438/952 (20130101); C08F 212/08 (20130101); C08F
212/08 (20130101); C08F 216/08 (20130101); C08F
220/1807 (20200201); C08F 220/20 (20130101) |
Current International
Class: |
G03F
7/11 (20060101); C08K 5/07 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 789 278 |
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Aug 1997 |
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EP |
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0 794 458 |
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Sep 1997 |
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EP |
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0 583 205 |
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Aug 1998 |
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EP |
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0 987 600 |
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Nov 2003 |
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EP |
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59-8770 |
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Jan 1984 |
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JP |
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2002-14791 |
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Jan 2002 |
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JP |
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WO 97/33198 |
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Sep 1997 |
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WO |
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WO 00/17712 |
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Mar 2000 |
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WO |
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WO 00/67072 |
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Sep 2000 |
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WO |
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WO 2004/040369 |
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May 2004 |
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WO |
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WO 2006/030320 |
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Mar 2006 |
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WO |
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WO 2006/085220 |
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Aug 2006 |
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WO |
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Other References
English language abstract of JP 59-8770. cited by other .
English language abstract of JP 2002-14791 A. cited by other .
Notification of Transmittal of the International Search Report and
Written Opinion of the International Searching Authority, or the
Declaration (Form PCT/ISA/220), the International Search Report
(Form PCT/ISA/210), and the Written Opinion of the International
Search Authority (Form PCT/ISA/237) for PCT/IB2005/003232, which
corresponds to U.S. Appl. No. 11/159,002. cited by other .
Office Action from U.S. Appl. No. 11/159,002. cited by other .
Iwasa, et al., "Novel negative photoresist based on polar
alicycllic polymers for ArF excimer laser lithography", SPIE vol.
3333, pp. 417-424, 1998, XP002369065. cited by other .
Notification Concerning Transmittal of Copy of International
Preliminary Report on Patentability (Chapter I of the Patent
Cooperation Treaty) (Form PCT/IB/326), International Preliminary
Report on Patentability (Form PCT/IB/373), and Written Opinion of
the International Searching Authority (Form PCT/ISA/237) for
PCT/IB2006/003074. cited by other .
Notification of Transmittal of the International Search Report and
the Written Opinion of the International Searching Authority, or
the Declaration (Form PCT/ISA/220) for PCT/IB2006/003074, submitted
Jan. 16, 2009. cited by other .
International Search Report (Form PCT/ISA/210) for
PCT/IB2006/003074, submitted Jan. 16, 2009. cited by other .
Written Opinion of the International Searching Authority (Form
PCT/ISA/237) for PCT/IB2006/003074, submitted Jan. 16, 2009. cited
by other .
Takei, S. et al., "New advanced BARC and gap fill materials based
on sublimate reduction for 193nm lithography", Proceedings of the
SPIE, vol. 6153, pp. 6513Q1-6513Q10 (2006), Mar. 2006. cited by
other .
Trefonas P. et al., "Organic antireflective Coatings for 193nm
Lithography", Proceedings of the SPIE, vol. 3678, pp. 2-12 (1999).
cited by other .
Xu, G. et al., "New Antireflective Coatings for 193 nm
Lithography", Proceedings of the SPIE, vol. 3333, pp. 524-531
(1998). cited by other.
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Primary Examiner: Hamilton; Cynthia
Attorney, Agent or Firm: Jain; Sangya Kass; Alan P.
Claims
What invention claimed is:
1. A polymer consisting of the reaction product between
poly(hydroxyethyl methacrylate-co-benzyl methacrylate) and
N,N,N,N-tetra(methoxymethyl)glycoluril, wherein the polymer is
capable of self-crosslinking under acidic conditions.
2. An anti-reflective coating composition comprising (i) a polymer
selected from the group consisting of the reaction product between
poly(allyl alcohol-co-styrene) and
N,N,N,N-tetra(methoxymethyl)glycoluril and the reaction product
between poly(hydroxyethyl methacrylate-co-benzyl methacrylate) and
N,N,N,N-tetra(methoxymethyl)glycoluril, wherein the polymer is
capable of self-crosslinking under acidic conditions, (ii) a
solvent; and a thermal acid generator.
3. The composition of claim 2 wherein for (i), the polymer is the
reaction product between poly(allyl alcohol-co-styrene) and
N,N,N,N-tetra(methoxymethyl)glycoluril.
4. The composition of claim 2 wherein for (i), the polymer is the
reaction product between poly(hydroxyethyl methacrylate-co-benzyl
methacrylate) and N,N,N,N-tetra(methoxymethyl)glycoluril.
Description
BACKGROUND OF THE INVENTION
The present invention relates to novel polymers and their use in
antireflective coating compositions in reducing outgassing.
Photoresist compositions are used in microlithography processes for
making miniaturized electronic components such as in the
fabrication of computer chips and integrated circuits. Generally,
in these processes, a thin coating of film of a photoresist
composition is first applied to a substrate material, such as
silicon wafers used for making integrated circuits. The coated
substrate is then baked to evaporate any solvent in the photoresist
composition and to fix the coating onto the substrate. The baked
coated surface of the substrate is next subjected to an image-wise
exposure to radiation.
This radiation exposure causes a chemical transformation in the
exposed areas of the coated surface. Visible light, ultraviolet
(UV) light, electron beam and X-ray radiant energy are radiation
types commonly used today in microlithographic processes. After
this image-wise exposure, the coated substrate is treated with a
developer solution to dissolve and remove either the
radiation-exposed or the unexposed areas of the photoresist.
The trend towards the minitiarization of semiconductor devices has
led to the use of sophisticated multilevel systems to overcome
difficulties associated with such minitiarization. The use of
highly absorbing antireflective coatings in photolithography is a
simpler approach to diminish the problems that result from back
reflection of light from highly reflective substrates. Two
deleterious effects of back reflectivity are thin film interference
and reflective notching. Thin film interference results in changes
in critical linewidth dimensions caused by variations in the total
light intensity in the resist film as the thickness of the resist
changes. Variations of linewidth are proportional to the swing
ratio (S) and therefore must be minimized for better linewidth
control. Swing ratio is defined by:
S=4(R.sub.1R.sub.2).sup.1/2e.sup.-.alpha.D where,
R.sub.1 is the reflectivity at the resist/air or resist/top coat
interface, R.sub.2 is the reflectivity at the resist/substrate
interface, a is the resist optical absorption coefficient, and D is
the resist film thickness.
Antireflective coatings function by absorbing the radiation used
for exposing the photoresist, that is, reducing R.sub.2, and
thereby reducing the swing ratio. Reflective notching becomes
severe as the photoresist is patterned over substrates containing
topographical features, which scatter light through the photoresist
film, leading to linewidth variations, and in the extreme case,
forming regions with complete resist loss.
Organic antireflective coatings are usually cured at temperatures
above 180.degree. C. Thus, small molecules tend to sublime out of
the film during the cure. Outgassing of low molecular weight
components is a problem for antireflective coatings in that the
components tends to accumulate in bake ovens and in their exhaust
plumbing. Sublimed materials can create defects on substrates if
dislodged from surfaces on which they accumulated. The current
invention uses polymers that are capable of self-crosslinking,
which removes the need for low molecular weight crosslinkers.
SUMMARY OF THE INVENTION
The present invention relates to a polymer comprising a first
repeat unit derived from an ethylenically unsaturated compound
containing a pendant active hydrogen and a second repeat unit which
is copolymerizable with the first repeat unit, with at least 10 mol
% of the pendant active hydrogen in the polymer being replaced with
an aminoplast, wherein the polymer self-crosslinks under acidic
conditions. The present invention also relates to the use of the
novel polymer in a solvent to comprise an antireflective coating
composition. The antireflective coating can optionally contain an
acid generator. The polymer in the antireflective coating further
comprises a repeating unit with an absorbing chromophore. The
repeating unit containing an absorbing chromophore can be the first
repeat unit, the second repeat unit, or an additional monomer.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a polymer comprising a first
repeat unit derived from an ethylenically unsaturated compound
containing a pendant active hydrogen and a second repeat unit which
is copolymerizable with the first repeat unit, with at least 10 mol
% of the pendant active hydrogen in the polymer being replaced with
an aminoplast, wherein the polymer self-crosslinks under acidic
conditions.
The present invention also relates to the use of the novel polymer
in a solvent to comprise an antireflective coating composition. The
antireflective coating can optionally contain an acid generator.
The polymer in the antireflective coating further comprises a
repeating unit with an absorbing chromophore. The repeating unit
containing an absorbing chromophore can be the first repeat unit,
the second repeat unit, or an additional monomer.
As the ethylenically unsaturated compound of the first repeat unit,
there may be mentioned a polymerizable compound having a pendant
active hydrogen. Examples of the ethylenically unsaturated compound
include, but are not limited to, for example, hydroxy containing
acrylate monomers such as, for example, hydroxy ethyl acrylate,
hydroxy propyl acrylate, hydroxy ethylhexyl acrylate, hydroxy butyl
acrylate, hydroxy isodecyl acrylate, hydroxy lauryl acrylate,
diethylene glycol monoacrylate, 2-hydroxy-3-phenoxypropyl acrylate,
etc., and hydroxy containing methacrylate monomers corresponding to
the above-mentioned acrylates, for example, hydroxy ethyl
methacrylate, hydroxy propyl methacrylate, hydroxy ethylhexyl
methacrylate, hydroxy butyl methacrylate, hydroxy isodecyl
methacrylate, hydroxy lauryl methacrylate, diethylene glycol
monomethacrylate, 2-hydroxy-3-phenoxypropyl methacrylate, etc.;
allylic monomers, such as, for example, allyl alcohol, methallyl
alcohol, alkoxylation products of allyl alcohol and methallyl
alcohol with ethylene oxide, propylene oxide, and the like, and
mixtures thereof, examples of which include allyl alcohol
monopropoxylate and allyl alcohol monoethoxylate; styrene
derivatives such as p-hydroxystyrene, m-hydroxystyrene,
o-hydroxystyrene, .alpha.-methyl-p-hydroxystyrene,
4-hydroxy-2-methylstyrene, 4-hydroxy-3-methylstyrene,
3-hydroxy-2-methylstyrene, 3-hydroxy-4-methylstyrene,
3-hydroxy-5-methylstyrene; amino group-substituted monomers include
aminoethyl acrylate, t-butyl aminoethyl methacrylate, aminoethyl
acrylate, aminoethyl methacrylate, 2-methyl aminoethyl
methacrylate, 3-aminopropyl methacrylate, 4-aminocyclohexyl
methacrylate, and 4-aminostyrene, etc.; carboxylic acid
group-substituted monomers include acrylic acid, methacrylic acid,
crotonic acid, vinylacetic acid and the like, etc.; sulfonic acid
group-substituted monomers include vinylsulfonic acid,
styrenesulfonic acid, vinylbenzylsulfonic acid, methallylsulfonic
acid and the like, etc., as well as the corresponding sulfonamides,
and the like, etc.
As the second repeat unit, there may be mentioned, for example,
aromatic vinyl compounds, such as styrene, a-methylstyrene,
4-methylstyrene, m-methylstyrene, 4-acetoxystyrene,
4-carboxystyrene, 4-aminostyrene, 4-methoxystyrene,
1,3-dimethylstyrene, tertbutylstyrene, vinylnaphthalene, and the
like, etc.; alkyl methacrylates such as methyl methacrylate, ethyl
methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl
methacrylate, cyclohexyl methacrylate, octyl methacrylate, dodecyl
methacrylate, etc.; vinyl ethers such as ethyl vinyl ether, propyl
vinyl ether, butyl vinyl ether, octyl vinyl ether, methoxyethyl
vinyl ether, ethoxyethyl vinyl ether, hydroxyethyl vinyl ether,
benzyl vinyl ether, tetrahydrofurfuryl vinyl ether, phenyl vinyl
ether, tolyl vinyl ether and the like, etc.; alkyl acrylates such
as methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate,
2-ethylhexyl acrylate, cyclohexyl acrylate, octyl acrylate, dodecyl
acrylate, etc.; aryl methacrylates or alkylaryl methacrylates such
as phenyl methacrylate, benzyl methacrylate; aryl acrylates or
alkylaryl acrylates such as phenyl acrylate, benzyl acrylate; vinyl
ethers and esters, etc. In essence, it is possible to use any other
monomer customarily used for the preparation of polymers used in
antireflective compositions that does not contain a pendent active
hydrogen and which can polymerize with the first repeat unit as the
second repeat unit.
Additionally, additional monomers, different or the same as the
second repeat unit, can be made part of the polymer to form, for
example, terpolymers, tetrapolymers, and the like.
When the polymers of the present invention are used in
antireflective compositions, absorption of the antireflective
composition may be as an absorbing chromophore in the polymer or as
an additive dye. It is preferred to use an absorbing chromophore in
the polymer as it reduces the potential for additional volatile
components in the composition.
Examples of an absorbing chromophore are hydrocarbon aromatic
moieties and heterocyclic aromatic moieties with from one to four
separate or fused rings, where there are 3 to 10 atoms in each
ring. Examples of monomers with absorbing chromophores that can be
polymerized with the first repeat unit and the second repeat unit
include vinyl compounds containing substituted and unsubstituted
phenyl, substituted and unsubstituted anthracyl, substituted and
unsubstituted phenanthryl, substituted and unsubstituted naphthyl,
substituted and unsubstituted heterocyclic rings containing
heteroatoms such as oxygen, nitrogen, sulfur, or combinations
thereof, such as pyrrolidinyl, pyranyl, piperidinyl, acridinyl,
quinolinyl. Other chromophores are described in U.S. Pat. Nos.
6,114,085, 5,652,297, 5,981,145, 5,939,236, 5,935,760 and
6,187,506, which may also be used, and are incorporated herein by
reference. The preferred chromophores are vinyl compounds of
substituted and unsubstituted phenyl, substituted and unsubstituted
anthracyl, and substituted and unsubstituted naphthyl; and more
preferred monomers are styrene, hydroxystyrene, acetoxystyrene,
vinyl benzoate, vinyl 4-tert-butylbenzoate, ethylene glycol phenyl
ether acrylate, phenoxypropyl acrylate,
2-(4-benzoyl-3-hydroxyphenoxy)ethyl acrylate,
2-hydroxy-3-phenoxypropyl acrylate, phenyl methacrylate, benzyl
methacrylate, 9-anthracenylmethyl methacrylate, 9-vinylanthracene,
2-vinyinaphthalene, N-vinylphthalimide, N-(3-hydroxy)phenyl
methacrylamide, N-(3-hydroxy-4-nitrophenylazo)phenyl
methacrylamide, N-(3-hydroxyl-4-ethoxycarbonylphenylazo)phenyl
methacrylamide, N-(2,4-dinitrophenylaminophenyl)maleimide,
3-(4-acetoaminophenyl)azo-4-hydroxystyrene,
3-(4-ethoxycarbonylphenyl)azo-acetoacetoxy ethyl methacrylate,
3-(4-hydroxyphenyl)azo-acetoacetoxy ethyl methacrylate,
3-(4-nitrophenyl)azoacetoacetoxy ethyl methacrylate, benzyl
methacrylate, and 3-(4-methoxycarbonylphenyl)azoacetoacetoxy ethyl
methacrylate.
In some instances, the monomer containing the absorbing chromophore
can be the same as the first repeat unit; for example,
hydroxystyrene, which contains both an absorbing chromophore
component and a pendant active hydrogen. In this case, the second
repeat unit can be any other monomer that can polymerize with
hydroxystyrene. In other instances where the first repeat unit only
has a pendant active hydrogen, then the second repeat unit can be
any monomer that polymerizes with the first repeat unit, in which
case an additional monomer unit containing an absorbing chromophore
would have be added, or the second repeat unit can be any monomer
that polymerizes with the first repeat unit as well as containing
an absorbing chromophore (for example, styrene or benzyl
methacrylcate, and the like), in which case an additional monomer
containing an absorbing chromophore would be optional. It is
preferable that when the first repeat unit only has a pendant
active hydrogen, the second repeat unit contains an absorbing
chromophore.
In still other instances, it may be beneficial to add a polyol
during the reaction when the active hydrogen on the first repeat
unit is replaced by an aminoplast. The addition of the polyol can
reduce the k value, absorption parameter, of films formed by the
antireflective composition. Examples of useful polyols are shown
below.
##STR00001##
Poly[trimethylolpropane/di(propylene glycol)-alt-adipic
acid/phthalic anhydride], average M.sub.n.about.500
##STR00002##
Poly[di(ethylene glycol)/glycerol-alt-adipic acid], average
M.sub.n.about.2,500
##STR00003##
Poly[di(ethylene glycol)/trimethylolpropane-alt-adipic acid],
average M.sub.n.about.2,300
The term hydrocarbyl as employed herein means any unsubstituted or
substituted aliphatic, cycloaliphatic, aromatic, or aryl groups and
any combination thereof.
Alkoxyalkyl refers to an alkoxy group, as defined herein, appended
to an alkyl group, as defined herein. Exemplary alkoxyalkyl groups
include methoxymethyl, methoxyethyl, isopropoxymethyl, and the
like.
Alkylol refers to a hydroxy group, as defined herein, appended to
an alkyl group (alkyl refers to branched or straight chain acyclic
alkyl group comprising one to about twenty carbon atoms (preferably
one to about eight carbon atoms, more preferably one to about six
carbon atoms). Exemplary lower alkyl groups include methyl, ethyl,
n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, pentyl,
neopentyl, iso-amyl, hexyl, octyl, and the like.)
The polymer of the present invention can have as the first repeat
unit a formula
##STR00004## wherein R is the recurring first repeat unit moiety
which is part of the polymer backbone;
L is a linking group; and
T is CO.sub.2, CSO, O, S, NR.sub.7, CONR.sub.7, SO.sub.3, PO.sub.3,
or SO.sub.2NR.sub.7 wherein R.sub.7 is a hydrocarbyl radical
hydrogen, where at least 10 mol % of H is replaced with an
aminoplast.
L, as a linking group, includes divalent hydrocarbon radicals such
as: alkylene, cycloalkylene, arylene, aralkylene, or alkarylene
radicals containing from 1 to 20 carbon atoms, more preferably from
2 to 12 carbon atoms.
Alkylene refers to a divalent group derived from a straight or
branched chain saturated hydrocarbon having from 1 to 20 carbon
atoms by the removal of two hydrogen atoms, for example
--CH.sub.2--, --CH.sub.2CH.sub.2--, --CH(CH.sub.3)--,
--CH.sub.2CH.sub.2CH.sub.2--, --CH.sub.2C(CH.sub.3).sub.2CH.sub.2--
and the like.
Cycloalkylene refers to mono- or bicyclic divalent ring-containing
groups containing in the range of about 3 up to about 15 carbon
atoms which can be unsubstituted or substituted by one or more
substituents as set forth below.
Arylene refers to divalent aromatic groups typically having in the
range of 6 up to 14 carbon atoms which can be unsubstituted or
substituted by one or more substituents as set forth below.
Alkarylene refers to alkyl-substituted divalent aryl groups
typically having in the range of about 7 up to 16 carbon atoms
which can be unsubstituted or substituted by one or more
substituents as set forth below.
Aralkylene refers to aryl-substituted divalent alkyl groups
typically having in the range of about 7 up to 16 carbon atoms
which can be unsubstituted or substituted by one or more
substituents as set forth below.
Aryl as used herein refers to a mono- or bicyclic carbocyclic ring
system having one or two aromatic rings including, but not limited
to, phenyl, naphthyl, tetrahydronaphthyl, indanyl, indenyl and the
like, which can be unsubstituted or substituted by one or more
substituents as set forth below.
The above groups can be unsubstituted or substituted with
substituents independently selected from loweralkyl, halo,
haloalkyl, haloalkoxy, hydroxyalkyl, alkenyloxy, alkoxy,
alkoxyalkoxy, alkoxycarbonyl, alkoxycarbonylalkenyl,
(alkoxycarbonyl)thioalkoxy, thioalkoxy, amino, alkylamino,
dialkylamino, aminoalkyl, trialkylaminoalkyl, aminocarbonyl,
aminocarbonylalkoxy, alkanoylamino, arylalkoxy, aryloxy, mercapto,
cyano, nitro, carboxaldehyde, carboxy, carboxyalkenyl,
carboxyalkoxy, alkylsulfonylamino, cyanoalkoxy,
(heterocyclic)alkoxy, hydroxy, hydroxalkoxy, phenyl and
tetrazolylalkoxy. In addition, substituted aryl groups include
tetrafluorophenyl and pentafluorophenyl.
Examples of L include phenylene, biphenylene, naphthylene,
methylene, ethylene, 1,3-propylene, 1,4-butylene, phenylmethylene
(--C.sub.6H.sub.4--CH.sub.2--). The divalent hydrocarbon portion of
L may be further substituted with radicals that do not interfere
with the coupling function of the active hydrogen moiety. Preferred
examples of such non-interfering substituents are alkyl, aryl,
alkyl- or aryl-substituted silyl radicals, and fluoro
substituents.
Other examples of L include --C(.dbd.O)O--(CH.sub.2).sub.n-- where
n is an integer from 1 to 10.
The group T-H in the previous formula thus may be --COOH, --CSOH,
--OH, --SH, --CONR.sub.7H, --SO.sub.3H, --PO.sub.3H,
--SO.sub.2NR.sub.7H or --NR.sub.7H group, wherein R preferably is a
C.sub.1-18, preferably a C.sub.1-10 hydrocarbyl radical or
hydrogen, and H is hydrogen. Preferred R.sub.7 groups are alkyls,
cycloalkyls, aryls, arylalkyls, or alkylaryls of 1 to 18 carbon
atoms, more preferably those of 1 to 12 carbon atoms. Most
preferably, the group T-H is --OH or --NR.sub.7H.
Examples of aminoplasts useful in the present invention include
those, such as, for example, glycoluril-formaldehyde resins,
melamine-formaldehyde resins, benzoguanamine-formaldehyde resins,
and urea-formaldehyde resins.
Monomeric, methylated glycoluril-formaldehyde resins are useful for
preparing thermosetting polyester anti-reflective coatings which
can be used in conjunction with acid-sensitive photoresists.
Glycoluril-formaldehyde resins can have a formula
##STR00005## wherein Y is selected from H, an alkyl group of from 1
to 20 carbon atoms, an aryl group of from 6 to 20 carbon atoms, and
an aralkyl group of from 7 to 20 carbon atoms, and wherein each
R.sub.8 is independently selected from H, an alkylol group and an
alkoxyalkyl group.
One example is N,N,N,N-tetrahydroxymethylglycoluril (when R.sub.8
is alkylol) and another is N,N,N,N-tetra(alkoxymethyl)glycoluril
(when R.sub.8 is alkoxyalkyl). Examples of
N,N,N,N-tetra(alkoxymethyl)glycoluril, may include, e.g.,
N,N,N,N-tetra(methoxymethyl)glycoluril,
N,N,N,N-tetra(ethoxymethyl)glycoluril,
N,N,N,N-tetra(n-propoxymethyl)glycoluril,
N,N,N,N-tetra(i-propoxymethyl)glycoluril,
N,N,N,N-tetra(n-butoxymethyl)glycoluril and
N,N,N,N-tetra(t-butoxymethyl)glycoluril.
N,N,N,N-tetra(methoxymethyl)glycoluril is available under the
trademark POWDERLINK from Cytec Industries (e.g., POWDERLINK 1174).
Other examples include methylpropyltetramethoxymethyl glycoluril,
and methylphenyltetramethoxymethyl glycoluril. Similar materials
are also available under the NIKALAC tradename from Sanwa Chemical
(Japan).
Other aminoplast crosslinking agents are commercially available
from Cytec Industries under the trademark CYMEL and from Monsanto
Chemical Co. under the trademark RESIMENE. Some of other aminoplast
crosslinking agents examples of such compounds are formaguanamine,
acetoguanamine, methylolbenzoguanamine or alkyl ether compound
thereof, such as tetramethylolbenzoguanamine,
tetramethoxymethylbenzoguanamine and
trimethoxymethylbenzoguanamine;
2,6-bis(hydroxymethyl)4-methylphenol or alkyl ether compound
thereof.
Other possible crosslinking agents include methylolmelamines, such
as hexamethylolmelamine, pentamethylolmelamine, and
tetramethylolmelamine as well as etherified amino resins, for
example alkoxylated melamine resins (for example,
hexamethoxymethylmelamine, pentamethoxymethylmelamine,
hexaethoxymethylmelamine, hexabutoxymethylmelamine and
tetramethoxymethylmelamine). Various melamine and urea resins are
commercially available under the Nikalacs (Sanwa Chemical Co.),
Plastopal (BASF AG), or Maprenal (Clariant GmbH) tradenames.
The thermal acid generator of the present invention, when used, is
a compound which, when heated to temperatures greater than
90.degree. C. and less than 250.degree. C., generates an acid. The
acid, together with the crosslinker, crosslinks the polymer. The
antireflective film after heat treatment becomes insoluble in the
solvents used for coating photoresists, and furthermore, is also
insoluble in the alkaline developer used to image the photoresist.
Preferably, the thermal acid generator is activated at 90.degree.
C. and more preferably at 150.degree. C., and even more preferably
at 190.degree. C. The antireflective film is heated for a
sufficient length of time to crosslink the coating. Examples of
thermal acid generators include, but are not limited to, onium
salts, benzoin tosylates,
tris(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione,
2,4,4,6-tetrabromocyclohexadienone, cyclohexyl p-toluenesulfonates,
menthyl p-toluenesulfonates, bornyl p-toluenesulfonates, cyclohexyl
triisopropylbenzenesulfonates, cyclohexyl 4-methoxybenzene
sulfonates, 2,1,4 diazonaphthoquinone esters of multihydroxy
phenolic compounds, nitrobenzyl tosylates, such as 2-nitrobenzyl
tosylate, 2,4-dinitrobenzyl tosylate, 2,6-dinitrobenzyl tosylate,
4-nitrobenzyl tosylate; nitrobenzyl benzenesulfonates such as
2-trifluoromethyl-6-nitrobenzyl 4-chlorobenzenesulfonate, as
2-trifluoromethyl-6-nitrobenzyl 4-nitro benzenesulfonate; phenolic
sulfonate esters such as phenyl-4-methoxybenzenesulfonate, aromatic
sulfonamides, alkyl and aryl phosphoric acids esters, and other
aryl and alkyl esters and amine salts of organic sulfonic acids
such as dodecylbenzylsulfonium triethylammonium salt
(DDBSA:Et.sub.3N). Compounds that generate a sulfonic acid upon
activation are generally suitable.
Thermal acid generators are preferred over free acids, although
free acids may also be used, in the novel antireflective
composition, since it is possible that over time the shelf
stability of the antireflective solution will be affected by the
presence of the acid, if the polymer were to crosslink in solution.
Thermal acid generators are only activated when the antireflective
film is heated on the substrate.
Typically a thermal acid generator is present in an antireflective
composition in concentration of from about 0 to 10% percent by
weight, preferably from about 0.1 to 7.0 percent weight of the
total of the dry components of the composition, and more preferably
from about 0.1 to 5.0 percent weight of the total of the dry
components of the composition.
The process used for polymerization can be any of the ones known in
the art for polymerizing vinyl polymers, such as, ionic or free
radical polymerization. The polymer structure formed can be
composed of alternate, block or random copolymers. The weight
average molecular weight of the polymer ranges from about 500 to
about 1,000,000, preferably from about 1,000 to about 100,000, and
more preferably from about 2,000 to about 40,000.
The monomers can be polymerized in an organic solvent, where the
solvent is the same as the casting solvent of the antireflective
coating, preferably PGMEA, PGME or ethyl lactate.
The coating composition comprises the polymer of the instant
invention and a suitable solvent or mixtures of solvents. Other
components may be added to enhance the performance of the coating,
e.g. monomeric, polymeric and/or a mixture of monomeric and
polymeric dyes, lower alcohols, surface leveling agents, adhesion
promoters, antifoaming agents etc., all of which are well known to
those skilled in the art.
The absorption of the antireflective coating can be optimized for a
certain wavelength or range of wavelengths by the suitable choice
of substituents on the dye functionality. Using substituents that
are electron-withdrawing or electron donating generally shifts the
absorption wavelength to longer or shorter wavelengths
respectively. In addition, the solubility of the antireflective
polymer in a particularly preferred solvent can be adjusted by the
appropriate choice of substituents on the monomer.
The polymer of the antireflective coating composition is present in
the range of about 1% to about 40% by total weight of solution. The
exact weight used is dependent on the molecular weight of the
polymer and the film thickness of the coating desired. Typical
solvents, used as mixtures or alone, that can be used are propylene
glycol monomethyl ether (PGME), propylene glycol monomethyl
etheracetate (PGMEA), ethyl lactate, cyclopentanone, cyclohexanone,
oxyisobutyric acid esters, for example,
methyl-2-hydroxyisobutyrate, and gamma butyrolactone. Solvents with
a lower degree of toxicity, and good coating and solubility
properties are generally preferred.
Since the antireflective film is coated on top of the substrate and
is further subject to dry etching it is envisioned that the film is
of sufficiently low metal ion level and purity that the properties
of the semiconductor device are not adversely affected. Treatments
such as passing a solution of the polymer through an ion exchange
column or a combination of anion and cation exchange columns,
filtration, and an extraction process can be used to reduce the
concentration of metal ions and to reduce particles. Metal ion
levels in the polymer below 50 ppb each metal are preferred, below
10 ppb are more preferred and below 1 ppb are even more
preferred.
The antireflective coating composition is coated on the substrate
using techniques well known to those skilled in the art, such as
dipping, spin coating or spraying. The film thickness of the
antireflective coating typically ranges from about 0.01 micron to
about 1 micron. Thicker coatings, especially up to 10 microns, can
also be used if necessary, especially for planarization of
substrates with topography. The coating is further heated on a hot
plate or convection oven to remove any residual solvent and to
insolubilize the film.
Photoresists coated over the antireflective film can be any of the
types used in the semiconductor industry.
There are two types of photoresist compositions, negative-working
and positive-working. When negative-working photoresist
compositions are exposed image-wise to radiation, the areas of the
resist composition exposed to the radiation become less soluble to
a developer solution (e.g. a cross-linking reaction occurs) while
the unexposed areas of the photoresist coating remain relatively
soluble to such a solution. Thus, treatment of an exposed
negative-working resist with a developer causes removal of the
non-exposed areas of the photoresist coating and the creation of a
negative image in the coating. Thereby uncovering a desired portion
of the underlying substrate surface on which the photoresist
composition was deposited.
On the other hand, when positive-working photoresist compositions
are exposed image-wise to radiation, those areas of the photoresist
composition exposed to the radiation become more soluble to the
developer solution (e.g. a rearrangement reaction occurs) while
those areas not exposed remain relatively insoluble to the
developer solution. Thus, treatment of an exposed positive-working
photoresist with the developer causes removal of the exposed areas
of the coating and the creation of a positive image in the
photoresist coating. Again, a desired portion of the underlying
surface is uncovered.
Positive working photoresist compositions are currently favored
over negative working resists because the former generally have
better resolution capabilities. Photoresist resolution is defined
as the smallest feature which the resist composition can transfer
from the photomask to the substrate with a high degree of image
edge acuity after exposure and development. In many manufacturing
applications today, resist resolution on the order of less than one
micron are necessary. In addition, it is almost always desirable
that the developed photoresist wall profiles be near vertical
relative to the substrate. Such demarcations between developed and
undeveloped areas of the resist coating translate into accurate
pattern transfer of the mask image onto the substrate. This becomes
even more critical as the drive toward miniaturization reduces the
critical dimensions on the devices.
Positive-acting photoresists comprising novolak resins and
quinone-diazide compounds as photoactive compounds are well known
in the art. Novolak resins are typically produced by condensing
formaldehyde and one or more multi-substituted phenols, in the
presence of an acid catalyst, such as oxalic acid. Photoactive
compounds are generally obtained by reacting multihydroxyphenolic
compounds with naphthoquinone diazide acids or their derivatives.
The sensitivity of these types of resists typically ranges from
about 300 nm to 440 nm.
High resolution, chemically amplified, deep ultraviolet (100-300
nm) positive and negative tone photoresists are available for
patterning images with less than quarter micron geometries. There
are two major deep ultraviolet (uv) exposure technologies that have
provided significant advancement in miniaturization, and these are
lasers that emit radiation at 248 nm and 193 nm. Examples of such
photoresists are given in the following patents and incorporated
herein by reference, U.S. Pat. No. 4,491,628, 5,350,660, EP 794458
and GB 2320718. Photoresists for 248 nm have typically been based
on substituted polyhydroxystyrene and its copolymers. On the other
hand, photoresists for 193 nm exposure require non-aromatic
polymers, since aromatics are opaque at this wavelength. Generally,
alicyclic hydrocarbons are incorporated into the polymer to replace
the etch resistance lost by eliminating the aromatic functionality.
Furthermore, at lower wavelengths the reflection from the substrate
becomes increasingly detrimental to the lithographic performance of
the photoresist. Therefore, at these wavelengths antireflective
coatings become critical.
The process of the instant invention further comprises coating a
substrate with the novel antireflective coating composition and
heating on a hotplate or convection oven at a sufficiently high
temperature for sufficient length of time to remove the coating
solvent in order to insolubilize the polymer to a sufficient extent
so as not to be soluble in the coating solvent of the photoresist
or in the aqueous alkaline developer. Various substrates known in
the art may be used, such as those that are planar, have topography
or have holes. The preferred range of temperature is from about
70.degree. C. to about 250.degree. C., preferably from about
100.degree. C. to about 200.degree. C. If the temperature is below
70.degree. C. then insufficient loss of solvent or insufficient
degree of insolubilization takes place and at temperatures above
250.degree. C. the polymer may become chemically unstable. The
exact temperature to be used is determined by the specific
application. A film of a photosensitive material is then coated on
top of the antireflective coating and baked to substantially remove
the photoresist solvent. The photoresist is imagewise exposed and
developed in an aqueous developer to remove the treated resist. An
optional heating step can be incorporated into the process prior to
development and after exposure. The process of coating and imaging
photoresists is well known to those skilled in the art and is
optimized for the specific type of resist used. The patterned
substrate is then dry etched. The etching may be carried out in a
suitable etch chamber to remove the exposed portions of the
antireflective film, with the remaining photoresist acting as an
etch mask. Optional heating steps may be included to optimize the
etching process. Various etching techniques known in the art may be
used.
The absorption parameter (k) of the novel composition ranges from
about 0.1 to about 1.0, preferably from about 0.15 to about 0.7 as
measured using ellipsometry. The refractive index (n) of the
antireflective coating is also optimized. The n and k values can be
calculated using an ellipsometer, such as the J. A. Woollam WVASE
VU-302 TM Ellipsometer. The exact values of the optimum ranges for
k and n are dependent on the exposure wavelength used and the type
of application. Typically for 193 nm the preferred range for k is
0.1 to 0.75, for 248 nm the preferred range for k is 0.15 to 0.8,
and for 365 nm the preferred range is from 0.1 to 0.8. The
thickness of the antireflective coating is less than the thickness
of the top photoresist. Preferably the film thickness of the
antireflective coating is less than the value of (wavelength of
exposure/refractive index), and more preferably it is less than the
value of (wavelength of exposure/(2 times refractive index)), where
the refractive index is that of the antireflective coating and can
be measured with an ellipsometer. The optimum film thickness of the
antireflective coating is determined by the exposure wavelength,
refractive indices of the antireflective coating and of the
photoresist, absorption characteristics of the top and bottom
coatings, and optical characteristics of the substrate. Since the
bottom antireflective coating must be removed by exposure and
development steps, the optimum film thickness is determined by
avoiding the optical nodes where no light absorption is present in
the antireflective coating.
An intermediate layer may be placed between the antireflective
coating and the photoresist to prevent intermixing, and is
envisioned as lying within the scope of this invention. The
intermediate layer is an inert polymer cast from a solvent, where
examples of the polymer are polysulfone and polyimides.
Another process that requires a bottom coat, such as the one of the
present invention, is one where the photosensitive layer can be
silylated to produce an etch resistant mask for etching the bottom
coat. Such a process comprises forming a coating on a substrate
with a bottom coat using the composition of the present invention,
forming a photosensitive layer, imaging and developing the
photosensitive layer, silylating this photosensitive layer with an
appropriate silylating agent, and etching the bottom coat using the
silylated photosensitive image as a mask. The concept of silylation
is known to those skilled in the art and is described in the
reference, Sebald et al, SPIE, Vol.1262, pages 528-537,1990. The
photoresist to be silylated is designed, as known in the art, to be
one capable of silylation. It has been found that the bottom coat
of this invention is especially well-suited to this process since
it has optimum etch properties.
Another process for which the present invention is useful is in
trilayer applications. For example, in 193-nm exposures, the
microchip industry typically uses roughly 270-350 nm of resist on
32-80 nm of bottom anti-reflective coating--so-called single layer
processing. For trilayer applications, photoresist thicknesses
(.about.150-200 nm) are much less than for single layer
applications, resulting in low aspect ratio lines. The trilayer
bottom anti-reflective coating instead is about 300-700 nm thick,
and the middle layer is about 30-215 nm thick. The advantages of
the trilayer resist processing include: (a) reduced resist aspect
ratios; (b) the ability to use conventional or ultra-thin
photoresists rather than silicon-containing and hydrophobic
(bilayer) resists; (c) minimized interaction of resist with the
substrate; (d) optimum thickness control for the imaging, masking,
and anti-reflective layer; and (e) improved depth-of-focus (DOF)
since the trilayer bottom anti-reflective coatings are designed to
be highly planarizing.
The following specific examples will provide detailed illustrations
of the methods of producing and utilizing compositions of the
present invention. These examples are not intended, however, to
limit or restrict the scope of the invention in any way and should
not be construed as providing conditions, parameters or values
which must be utilized exclusively in order to practice the present
invention.
Examples of antireflective formulations containing a self
crosslinking resin are shown below.
EXAMPLE 1
Reaction of Poly(allyl alcohol-co-styrene) with
N,N,N,N-tetra(methoxymethyl)glycoluril
20.0 g of poly(allyl alcohol-co-styrene) copolymer (Aldrich, Mw 2K,
allyl alcohol 33 mol %), 10.6 g
N,N,N,N-tetra(methoxymethyl)glycoluril (Powderlink 1174, Cytec
Industries), 0.15 g of p-toluenesulfonic acid (Aldrich), and 155 g
tetrahydrofuran (THF) was stirred at room temperature for 5 days.
The reaction product was precipitated by pouring the solution into
10000 mL distilled water, separated by vacuum filtration and dried
in a vacuum desiccator overnight to afford 17.8 g of white powdery
resin. Mw=5.2K (GPC/PS standard).
EXAMPLE 2
Antireflective Formulation
1.0 g of functionalized poly(allyl alcohol-co-styrene) resin from
Example 1, 0.01 g dodecylbenzylsulfonium triethylammonium salt
(DDBSA:Et.sub.3N), and 40.0 g 70/30 ArF-thinner (AZ Electronic
Materials USA Corp.) were combined and rolled overnight in a
plastic bottle and then passed through 0.2 .mu.m PTFE pore filters.
Spin casting followed by baking at 200.degree. C. for 60 seconds
resulted in a film that could not be removed after soaking in
ArF-thinner and maintain the same film thickness (FT) before and
after soaking. Variable Angle Spectroscopic Elipsometer FT 41 nm;
the optimized reflective index "n" at 193 nm was 1.81 and the
absorption parameter "k" was 0.76.
EXAMPLE 3
Synthesis of Poly(hydroxyethyl methacrylate-co-benzyl methacrylate)
(Abbreviated HB)
83.2 g of benzyl methacrylate, 25.8 g of hydroxyethyl methacrylate
(feed ratio of benzyl methacrylate/hydroxyethyl
methacrylate--80/20), 500 mL THF and 2 g AIBN were combined, in
that order, to a 1 L round bottom flask. The solution was refluxed
for 12 hr under nitrogen. After cooling, the polymer was recovered
by precipitation into 4 L of hexane, filtered and dried in a vacuum
desiccator. The polymer was produced in a 98.5% yield. Mw=30K
(GPC/PS standard).
EXAMPLE 4
Reaction of HB with N,N,N,N-tetra(methoxymethyl)glycoluril
7.2 g of the polymer from Example 3, 3.6 g
N,N,N,N-tetra(methoxymethyl)glycoluril (Powderlink 1174, Cytec
Industries), 0.054 g of p-toluenesulfonic acid (Aldrich), and 56 g
THF were stirred at room temperature for 2 days. The resulting
reaction product was precipitated in distilled water and dried in a
vacuum desiccator overnight to afford 6.7 g of white powdery resin.
Mw=34K (GPC/PS standard).
EXAMPLE 5
Antireflective Formulation
1.0 g of functionalized HB resin from Example 4, 0.01 g
dodecylbenzylsulfonium triethylammonium salt (DDBSA:Et.sub.3N), and
40 g 70/30 ArF-thinner (AZ Electronic Materials USA Corp.) were
combined and rolled overnight in a plastic bottle and then passed
through 0.2 .mu.m PTFE pore filters. Spin casting followed by
baking at 200.degree. C. for 60 seconds resulted in a film that
could not be removed after soaking in ArF-thinner and maintain the
same FT before and after soaking. Variable Angle Spectroscopic
Elipsometer FT 40 nm; the optimized reflective index "n" at 193 nm
was 1.86 and the absorption parameter "k" was 0.76.
* * * * *